Power-generating module with solar cell and method for fabricating the same

ABSTRACT

The invention discloses a power-generating module with solar cell and method for fabricating the same. The power-generating module includes a flexible substrate, a circuit and a solar cell. Both of the circuit and the solar cell are formed on the flexible substrate and are connected with each other, such that the solar cell is capable of providing the power needed by the circuit for operation.

FIELD OF THE INVENTION

The present invention is related to a power-generating module with solarcell and method for fabricating the same, and more particularly, theinvention to a power-generating module that integrates thin film solarcell and circuit unit and method for fabricating the same.

BACKGROUND OF THE INVENTION

In highly e-oriented era, all the tools needed in human life and workhave integrated with some kinds of electronic components. For example,computer, cellular phone, camera, automobile and motorcycle, a varietyof household appliance and manufacturing equipment, etc. Althoughe-oriented life has brought great convenience to human, due to the needof continuous power supply for the operation of electronic components,use of electrical power, such as battery or home/industrial level of DCor AC power is also increased accordingly.

Under the situation of limited traditional energy and easy generation ofpollution, there is a need for new pollution-free energy. Therefore,many related organizations have devoted to the development of windenergy, tidal energy and solar energy. Therefore, many kinds of relatedpower generating products have been developed, among them, theapplication in solar energy field is the most eye-catching one. With thedevelopment of semiconductor technology, a light and compact solar cellis now available in the market, in the mean time, it is integrated withsome electronic products to provide the power needed for the operationof the electronic products.

In addition, in order to simplify the process of electronic product,reduce the manufacturing cost and expand the application scope, flexiblesubstrate has been gradually introduced into the electronic product toreplace traditional substrate. For example, plastic substrate has beenused to replace the glass substrate in liquid crystal display tomanufacture flexible display such as electronic paper. Due to thelimited volume of such electronic products, if thin solar cells can beintegrated therein, it will be helpful to improve the entire designstructure and extending the utilization time.

However, the glass transition temperatures of the frequently usedflexible substrate today, such as poly ethylene naphthalate (PEN) andpoly ethylene terephthalate (PET) are 80° C. and 120° C. respectively.

This makes it difficult to take the high temperature in the process ofplasma-enhanced chemical vapor deposition (PECVD) for the fabrication ofsolar cells. In addition, if the temperature of the process of PECVD isreduced, for example, lower than 150° C., then the photovoltaicconversion efficiency of the solar cell will be very poor.

SUMMARY OF THE INVENTION

Accordingly, the scope of the invention is to provide a power-generatingmodule with solar cell to solve the above-mentioned problems of theprior art.

In an aspect of the invention, the power-generating module with solarcell includes: a flexible substrate, a circuit unit and a solar cellunit. Wherein, both of the circuit unit and the solar cell unit areformed on the flexible substrate and coupled to one another, so that thesolar cell unit can provide the power needed for the operation of thecircuit unit.

In one embodiment, the flexible substrate is polyethylene naphthalate(PEN) substrate, polyethylene terephthalate (PET) substrate or polyimidesubstrate. In one embodiment, the circuit unit can be thin filmtransistor made by inductive coupling plasma technology, and theelectron mobility thereof can be about 1.1 cm²/V-s.

In one embodiment, the solar cell unit further comprises: a first oxidelayer, a p-i-n multi-layer structure, a second oxide layer, a firstconductive layer and a second conductive layer. Wherein, the p-i-nmulti-layer structure is formed on the first oxide layer; the secondoxide layer is formed on the p-i-n multi-layer structure; the firstconductive layer is formed on the second oxide layer; and the secondconductive layer is formed on the first oxide layer.

In one embodiment, the first oxide layer is formed of transparentconducting oxide (TCO), and the second oxide layer is formed of IndiumTin Oxide (ITO). In one embodiment, the first conductive layer and thesecond conductive layer are formed of Aluminum. In one embodiment, thephotovoltaic conversion efficiency of the solar cell unit is about 9.6%.

Another scope of the invention is to provide a method for fabricating apower-generating module with solar cell to solve the above-mentionedproblems of the prior art.

In an aspect of the invention, the method includes the following stepsof: providing a flexible substrate; forming a solar cell unit on theflexible substrate by using a high density plasma at a temperature lowerthan 150° C.; and forming a circuit unit on the flexible substrate;wherein the solar cell unit is coupled to circuit unit to provide thepower needed for the operation of the circuit unit.

In one embodiment, the steps of forming the solar cell unit include thesteps of forming a p-type layer, an i-type layer and a n-type layersequentially, so as to form a p-i-n multi-layer structure. In practice,the process condition of the p-type layer includes a process pressurebetween 600 and 1200 mTorr, a process power between 30 and 60 W and adeposition rate between 2 and 5 A/s. In addition, the reaction gas toform the p-type layer includes SiH₄ having a flow rate between 6 and 15sccm; H₂ having a flow rate between 100 and 250 sccm; B₂H₆ having a flowrate between 0.5 and 1.5 sccm; and Ar having a flow rate between 100 and200 sccm.

In practice, the process condition of the i-type layer include a processpressure between 600 and 1200 mTorr, a process power between 15 and 40 Wand a deposition rate between 1 and 2.5 A/s. In addition, the reactiongas to form the i-type layer includes SiH₄ having a flow rate between 10and 20 sccm; H₂ having a flow rate between 100 and 250 sccm, and Arhaving a flow rate between 100 and 200 sccm.

In practice, the process condition of the n-type layer includes aprocess pressure between 600 and 1200 mTorr, a process power between 30and 60 W and a deposition rate between 2 and 4 A/s. In addition, thereaction gas to form the n-type layer includes SiH₄ having a flow ratebetween 6 and 15 sccm; H₂ having a flow rate between 100 and 250 sccm;PH₃ having a flow rate between 0.5 and 1.5 sccm, and Ar having a flowrate between 100 and 200 sccm.

By using the high density plasma technology to form the power-generatingmodule with solar cell, the invention has the following advantages of:low temperature growth, low ion bombardment, high deposition rate andenlargement of the area of the solar cell. Accordingly, thepower-generating module with solar cell of the invention can besuccessfully formed on the flexible substrate to show high conversionefficiency and high electron mobility.

For the advantages and spirit regarding the present invention, furtherunderstanding can be achieved through the following detailed descriptionand attached drawings of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of the power-generating modulewith solar cell according to one embodiment of the invention.

FIG. 2 illustrates a flow chart of the method of fabricating thepower-generating module with solar cell based on one embodiment of theinvention.

FIG. 3 illustrates the flow chart of step S400 in FIG. 2.

FIGS. 4A, 4B and 4C illustrate respectively charts made based on thep-type layer, i-type layer and n-type layer of one embodiment of theinvention.

FIGS. 5A and 5B illustrate the voltage, current density, wavelength andquantum efficiency of the amorphous silicon thin film solar cell unit ofone embodiment of the invention, the solar cell unit is formed by usinghigh density plasma technology at a process temperature of 140° C.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a power-generating module with solar cell and amethod for fabricating the same. In the followings, the embodiments andpractical applications of the invention are described in detail, so asto explain the features, spirit and advantages of the invention.

Please refer to FIG. 1, which illustrates the cross-sectional view ofone embodiment of the power-generating module with solar cell of thecurrent invention. As shown in the figure, the power-generating modulewith solar cell 1 of the invention mainly includes a flexible substrate10, a thin film transistor 12 and a solar cell unit 14.

Wherein, both of the thin film transistor 12 and the solar cell unit 14are formed on the flexible substrate 10. In practice, the flexiblesubstrate 10 can be, but not limited to PEN substrate, PET substrate orpolyimide substrate. In addition, the thin film transistor 12 of theembodiment can be replaced with any other suitable circuit unit, such asan electronic sensor and an electronic label, etc.

As shown in the figure, the thin film transistor 12 includes an activelayer 120, a source electrode structure 122, a drain electrode structure124, a gate electrode structure 126 and an insulating structure 128. Theactive layer 120 is formed on the flexible substrate 10; the sourceelectrode structure 122 and the drain electrode structure 124 are allformed on the active layer 120; and the gate electrode structure 126 isformed in between the source electrode structure 122 and the drainelectrode structure 124. The insulating structure 128 encloses theactive layer 120, the source electrode structure 122, the drainelectrode structure 124 and the gate electrode structure 126. Inaddition, the thin film transistor 12 can include several contactstructures (not shown), which are formed on the source electrodestructure 122, the drain electrode structure 124 and the gate electrodestructure 126 respectively, and exposed out of the insulating structure128. In practice, the insulating structure 128 can be made of SiO₂ orother suitable material.

As shown in the figure, the solar cell unit 14 includes: a metalliclayer 140, a first oxide layer 142, a p-i-n multi-layer structure 144, asecond oxide layer 146, a first conductive layer 148 a and a secondconductive layer 148 b.

Wherein, the metallic layer 140 is formed on the flexible substrate 10,and the metallic layer 140 can be made of Aluminum or other suitablematerial. The first oxide layer 142 is formed on the metallic layer 140,and the first oxide layer 142 can be made of transparent conductingoxide (TCO) or other suitable material.

The p-i-n multi-layer structure 144 is formed on the first oxide layer142. In addition, the p-i-n multi-layer structure 144 includes a n-typelayer 144 a, an i-type layer 144 b and a p-type layer 144 c. Inpractice, the n-type layer 144 a, the i-type layer 144 b and the p-typelayer 144 c can be hydrogenated amorphous silicon (a-Si:H) or othersuitable material.

Second oxide layer 146 is formed on the p-i-n multi-layer structure 144,and the second oxide layer 146 can be made of Indium Tin Oxide (ITO) orother suitable material. In addition, the first conductive layer 148 ais formed on the second oxide layer 146, and second conductive layer 148b is formed on the first oxide layer 142. In practice, the firstconductive layer 148 a and the second conductive layer 148 b can be madeof Aluminum or other suitable material.

Additionally, in practice, the solar cell unit 14 can be coupled to thethin film transistor 12 through circuit (not shown). The circuit can bea voltage and current control circuit, or other suitable circuit.

Please refer to FIG. 2, which shows a flow chart of the method offabricating the power-generating module with solar cell according to onepreferred embodiment of the invention. As shown in the figure, themethod includes the following steps:

Step S300, providing a flexible substrate, which can be PET, PEN,polyimide or other suitable substrate, as described above. Step S400,forming a solar cell unit on the flexible substrate by using a highdensity plasma at a temperature lower than 150° C. Step S500, forming acircuit unit on the flexible substrate, as described above, the circuitunit can be thin film transistor or other suitable circuit units. StepS600, coupling the solar cell unit to the circuit unit, so that thesolar cell unit can provide the power needed for the operation of thecircuit unit. Please note that, in practice, the order of theabove-mentioned steps can be optionally changed, and is not limited tothe embodiment.

Please refer to FIG. 3, which further illustrates a flow chart of S400of FIG. 2. As shown in the figure, step S400 can further includes thefollowing steps of:

Step S401, forming a metallic layer on the flexible substrate. Step S402forming a first oxide layer on the metallic layer. In practice, thefirst oxide layer can be formed by sputtering or other suitable method.Step 403, forming a n-type layer, an i-type layer and a p-type layer onthe first oxide layer sequentially by using high density plasma at atemperature lower than 150° C., to form a p-i-n multi-layer structure.

Step 404, forming a second oxide layer on the p-i-n multi-layerstructure. In practice, the second oxide layer can be formed bysputtering or other methods. Step S405, forming a first conductive layeron the second oxide layer. Step S406, etching the p-i-n multi-layerstructure so as to expose at least a part of the first oxide layer. StepS407, forming a second conductive layer above the exposed part of thefirst oxide layer.

Please note that, step S406 can be carried out optionally, or bereplaced with other step(s). Additionally, in practice, the firstconductive layer and the second conductive layer can be formed byelectron gun or other suitable method.

The process conditions of the above steps will be described in moredetail as follows.

Please refer to table 1, which lists the process parameters of the p-i-nmulti-layer structure of the solar cell.

The process conditions of the n-type layer include a process pressurebetween 600 and 1200 mTorr, a process power between 30 and 60 W, aprocess temperature between 60 and 150° C., and a deposition ratebetween 2 and 4 A/s. Meanwhile, in one embodiment, the n-type layer canbe formed of a reaction gas mixture including SiH₄, H₂, PH₃ and Ar,wherein the flow rate of SiH₄ is between 6 and 15 sccm, the flow rate ofH₂ is between 100 and 250 sccm, the flow rate of PH₃ is between 0.5 and1.5 sccm, and the flow rate of Ar is between 100 and 200 sccm.

The process conditions of the i-type layer include a process pressurebetween 600 and 1200 mTorr, a process power between 15 and 40 W, aprocess temperature between 60 and 150° C. and a deposition rate between1 and 2.5 A/s. Meanwhile, in one embodiment, the i-type layer can beformed of a reaction gas mixture including SiH₄, H₂ and Ar, wherein theflow rate of SiH₄ is between 10 and 20 sccm, the flow rate of H₂ isbetween 100 and 250 sccm, and the flow rate of Ar is between 100 and 200sccm.

The process conditions of the p-type layer include a process pressurebetween 600 and 1200 mTorr, a process power between 30 and 60 W, aprocess temperature between 60 and 150° C. and a deposition rate between2 and 5 A/s. Meanwhile, in one embodiment, the p-type layer can beformed of a mixture of reaction gas including SiH₄, H₂, B₂H₆ and Ar,wherein the flow rate of SiH₄ is between 6 and 15 sccm, the flow rate ofH₂ is between 100 and 250 sccm, the flow rate of B₂H₆ is between 0.5 and1.5 sccm, and the flow rate of Ar is between 100 and 200 sccm.

TABLE 1 Doping gas/flow SiH4:H2 rate Ar Pressure Dep. rate Layer (sccm)(sccm) (sccm) (mTorr) power Thickness (A/s) p 10:200 B2H6/1.3 200 900 5212 3.1 i 15:150 — 100 700 18 400 1.3 n 10:200  PH3/0.5 200 900 45 201.73

The characteristics of layers formed are illustrated sequentially inFIG. 4A (p-type layer), FIG. 4B (i-type layer) and FIG. 4C (n-typelayer).

The process conditions of the second oxide layer include a processpressure between 50 and 80 mTorr, a process power between 200 and 500 W,a process temperature between 80 and 150° C., and a deposition ratebetween 1 and 2 A/s. In addition, the etching conditions of step 406include a process pressure between 5 and 30 mTorr, and CF₄ with a flowrate between 150 and 200 sccm and Ar with a flow rate between 50 and 100sccm is used.

Please refer to FIGS. 5A and 5B, which shows, based on an embodiment ofthe invention, the voltage, current density, wavelength and quantumefficiency of an amorphous silicon thin film solar cell unit (with p-i-nmulti-layer structure having a thickness of 400 nm) deposited by usinghigh density plasma technology at a process temperature of 140° C. Inaddition, the photovoltaic conversion efficiency of the amorphoussilicon thin film solar cell unit is measured as 9.6%.

In another embodiment, when the amorphous silicon solar cell with thep-i-n multi-layer structure having a thickness of 300 nm is fabricatedunder process temperatures of 140° C., 90° C. and 60° C. respectively,the photovoltaic conversion efficiencies of the solar cell are 9.6%,6.9% and 4.6% respectively. In addition, from related experiments, theopen circuit voltage, fill factor, conversion efficiency and efficiencyspectrum of the solar cell are all shown to tend to be optimized withthe rising of temperature.

In addition, even if the process temperature is lowered to 60° C., thedark saturation current of the amorphous silicon thin film deposited byusing inductive plasma coupling technology can still be lower than6×10⁻⁸ A/cm². This proves that even under low temperature, the defectdensity of the amorphous thin film fabricated in the invention is stillvery low.

Through the confirmation of experiment, the Si thin film deposited byusing the method of the invention can be evenly deposited no matter onplanarized or roughening substrate, and no discontinuity or vacancy willbe generated on the interface between Si thin film and transparentconductive layer, so as to reach a extreme broad band quantum efficiencyspectrum (300 to 750 nm).

In practice, the thin film transistor of the invention can be formed, ata process temperature of 140° C., by using inductive coupling plasmatechnology. The electron mobility of the thin film transistor ismeasured to be about 1.1 cm2/V-s, and the thin film transistor can havea very high driving current. In addition, the thin film transistor canhave a very low dangling bond density, which results in a lowsub-threshold swing and low off-state current.

To sum up, because the power-generating module with solar cell of theinvention is formed by using high density plasma technology, it hasadvantages such as low temperature growth, low ion bombardment, highdeposition rate and enlargement of the area of the solar cell.Therefore, the power-generating module with solar cell of the inventioncan be successfully formed on the flexible substrate withcharacteristics such as high conversion efficiency and high electronmobility.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A power-generating module with solar cell, comprising: a flexiblesubstrate; a circuit unit, formed on the flexible substrate; and a solarcell unit, formed on the flexible substrate and coupled to the circuitunit, so as to provide the power needed for the operation of the circuitunit.
 2. The power-generating module with solar cell of claim 1, whereinthe flexible substrate is a PEN substrate, a PET substrate or apolyimide substrate.
 3. The power-generating module with solar cell ofclaim 1, wherein the circuit unit is a thin film transistor.
 4. Thepower-generating module with solar cell of claim 3, wherein the thinfilm transistor further comprises: an active layer, formed on theflexible substrate; a source electrode structure, formed on the activelayer; a drain electrode structure, formed on the active layer; and agate electrode structure, formed in between the source electrodestructure and the drain electrode structure.
 5. The power-generatingmodule with solar cell of claim 3, wherein the electron mobility of thethin film transistor is about 1.1 cm²/V-s.
 6. The power-generatingmodule with solar cell of claim 1, wherein the solar cell unit furthercomprises: a metallic layer, formed on the flexible substrate; a firstoxide layer, formed on the metallic layer; a p-i-n multi-layerstructure, formed on the first oxide layer; a second oxide layer, formedon the p-i-n multi-layer structure; a first conductive layer, formed onthe second oxide layer; and a second conductive layer, formed on thefirst oxide layer.
 7. The power-generating module with solar cell ofclaim 6, wherein the first oxide layer is formed of transparentconducting oxide (TCO), and the second oxide layer is formed of IndiumTin Oxide (ITO).
 8. The power-generating module with solar cell of claim6, wherein the p-i-n multi-layer structure is an hydrogenated amorphoussilicon structure.
 9. The power-generating module with solar cell ofclaim 1, wherein the photovoltaic conversion efficiency of the solarcell unit is about 9.6%.
 10. A method for fabricating a power-generatingmodule with solar cell, comprising the following steps of: providing aflexible substrate; forming a solar cell unit on the flexible substrateby using a high density plasma at a temperature lower than about 150°C.; and forming a circuit unit on the flexible substrate; wherein thesolar cell unit is coupled to the circuit unit, so as to provide thepower needed for the operation of the circuit unit.
 11. The method ofclaim 10, wherein forming the solar cell unit further comprises thefollowing steps of: (a) forming a metallic layer on the flexiblesubstrate; (b) forming a first oxide layer on the metallic layer; (c)forming a p-i-n multi-layer structure on the first oxide layer by usingthe high density plasma at a temperature lower than 150° C.; (d) forminga second oxide layer on the p-i-n multi-layer structure; (e) forming afirst conductive layer on the second oxide layer; and (f) forming asecond conductive layer on the first oxide layer.
 12. The method ofclaim 11, wherein the p-i-n multi-layer structure is a hydrogenatedamorphous silicon structure.
 13. The method of claim 11, furthercomprising the following steps in between step (e) and step (f): (e′)etching the p-i-n multi-layer structure to expose at least a part of thefirst oxide layer, and the second conductive layer of step (f) is formedon the exposed part of the first oxide layer.
 14. The method of claim11, wherein step (c) further comprises the following steps of: (c1)forming a n-type layer on the first oxide layer under a first processcondition, wherein the first process condition comprises a processpressure between 600 and 1200 mTorr, a process power between 30 and 60 Wand a deposition rate between 2 and 4 A/s; (c2) forming an i-type layeron the n-type layer under a second process condition, wherein the secondprocess condition comprises a process pressure between 600 and 1200mTorr, a process power between 15 and 40 W and a deposition rate between1 and 2.5 A/s; and (c3) forming a p-type layer on the i-type layer undera third process condition, wherein the third process condition comprisesa process pressure between 600 and 1200 mTorr, a process power between30 and 60 W and a deposition rate between 2 and 5 A/s.
 15. The method ofclaim 14, wherein in step (c1), the n-type layer is formed of a firstreaction gas mixture, which comprises SiH₄, H₂, PH₃ and Ar, wherein theflow rate of SiH₄ is between 6 and 15 sccm, the flow rate of H₂ isbetween 100 and 250 sccm, the flow rate of PH₃ is between 0.5 and 1.5sccm, and the flow rate of Ar is between 100 and 200 sccm.
 16. Themethod of claim 14, wherein in step (c2), the i-type layer is formed ofa second reaction gas mixture, which comprises SiH₄, H₂ and Ar, whereinthe flow rate of SiH₄ is between 10 and 20 sccm, the flow rate of H₂ isbetween 100 and 250 sccm, and the flow rate of Ar is between 100 and 200sccm.
 17. The method of claim 14, wherein in step (c3), the p-type layeris formed of a third reaction gas mixture, which comprises SiH₄, H₂,B₂H₆ and Ar, wherein the flow rate of SiH₄ is between 6 and 15 sccm, theflow rate of H₂ is between 100 and 250 sccm, the flow rate of B₂H₆ isbetween 0.5 and 1.5 sccm, and the flow rate of Ar is between 100 and 200sccm.
 18. The method of claim 11, wherein the first oxide layer isformed of transparent conducting oxide (TCO), and the second oxide layeris formed of Indium Tin Oxide (ITO).
 19. The method of claim 10, whereinthe flexible substrate is a PEN substrate, a PET substrate or apolyimide substrate.
 20. The method of claim 10, wherein the circuitunit is made of inductive coupling plasma technology.